Annular, elevated platforms which rotate are known. My Australian Pat. No. 674,637 discloses a method of construction of a platform which can be carried out on site. The method disclosed allows for part or all of the platform to be formed in one pour of concrete, with a means for providing a mould in an elevated position prior to the pouring.
However it has been found that there are some disadvantages to this method. Firstly, there can be undue stress placed on the concrete on one side of the centrally located beam (underneath the platform). This can occasionally lead to stress fractures or cracking of the concrete.
Also, with the manner of forming of the mould (preparatory to pouring the concrete to form the platform), nearly all of this must be done on site. Thus the equipment need for supporting the mould needs to be dismantled and transported from one site to the next. It is difficult to use this method of construction to prepare much of the form work off site. While it can be done, the method also means that the elements prepared off site, where possible, are often awkwardly shaped for shipment. Further, some duplication of otherwise re-usable elements is necessary.
Further, the moulding, if it remains under the platform, does not form an integral part of the platform and therefore does not add structural strength to the platform.
An object of the present invention is the provision of a method of construction of an elevated annular platform which overcomes the above described difficulties, and further provides a useful alternative to the presently available methods.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
For the purposes of this specification, an `elevated annular platform` is a platform which is up to two meters off the ground. It may be supported on one side with, for example, a base or support elements of the foundation underneath it. This support may be a support on the inner or outer side of the annulus, so that the outer or inner part of the platform is apparently cantilevered from the base or support elements of the foundation. The platform may be supported along under the center (that is, the center of the annulus of the platform) in addition to the above support, or instead of the above support. It may therefore be a free-standing platform with a circular support means under the platform. Such support may or may not rotate with part or all of the means of rotation of the platform, this means being secured to and/or located under the annulus.
Also for the purposes of this specification, the term `center line` is used to refer to the (imaginary) circle which falls at the center of the annulus of the platform, equidistant from the inner and outer edges of the annulus.